Disposable toothbrush assembly

ABSTRACT

A disposable toothbrush assembly comprising a disposable head having a hollow base which is open at one transverse end, slightly tapered along the longitudinal side wall edges and includes a plurality of bristles each of predetermined crosssectional configuration molded as an integral part of the base and projecting from the top surface thereof in an upward direction, the bristles defining a chimney along which toothpaste initially contained within the head is extruded after passing through a pre-cut port in the top wall of the head, the pre-cut port being closed by a hinged valve cover during storage prior to use. The toothbrush assembly also comprises a handle initially assembled during storage prior to use so as to extend a short distance into the head at the mentioned transverse opening, the handle having a slightly enlarged leading end, sized and shaped so as to spread the longitudinal side walls of the head during insertion, and including at the interface between the enlarged leading end and the adjacent remainder of the handle a notch along each side into which toothpaste flows during insertion to create a firm handle-retaining seal. The handle portion adjacent the mentioned enlarged leading end is sized and shaped so as to serve as a guide insuring proper alignment during insertion. An extrusion channel is defined along the top of the leading end and the alignment or guide portions of the handle to accommodate flow of toothpaste to the central port of the head after the leading end of the handle has passed the port site.

atent [1 1 [111 3,879,139 1 Apr. 22, 1975 DISPOSABLE TOOTHBRUSH ASSEMBLY[75] Inventors: Rulon R. Dahl, West .lordon;.

Garnett O'Brien Garrett, Salt Lake City, both of Utah [73] Assignee:Developmental Design, Inc., Salt Lake City, Utah [22] Filed: Feb. 25,1974 [21] Appl. N0.: 445,519

Related [1.8. Application Data [63] Continuation-in-part of Ser. No.363,232. May 23, 1973, abandoned, which is a continuation-in-part ofScr. No. 239,154, March 29, 1972, abandoned.

[52] US. Cl 401/135; 15/22 [51] Int. Cl A46b 11/02 [58] Field of Search401/132-135, 401/149, 150, 156, 171, 176, 182; 15/22, 176

[56] References Cited UNITED STATES PATENTS 1,947,720 2/1934 Laub 401/82,090,144 8/1937 Palimeri ct a1 401/135 3,181,189 5/1965 Leyden 15/22 R3,256,031 6/1966 Fillweber 15/22 R X 3,536,410 10/1970 Wargoe 401/132FORElGN PATENTS OR APPLICATIONS 512,130 7/1956 ltaly 401/176 PrimaryExaminer-Lawrence Charles Attorney, Agent, or Firm-Lynn G. Foster [57]ABSTRACT A disposable toothbrush assembly comprising a disposable headhaving a hollow base which is open at one transverse end, slightlytapered along the longitudinal side wall edges and includes a pluralityof bristles each of predetermined cross-sectional configuration moldedas an integral part of the base and projecting from the top surfacethereof in an upward direction, the bristles defining a chimney alongwhich toothpaste initially contained within the head is extruded afterpassing through a pre-cut port in the top wall of the head, the pre-cutport being closed by a hinged valve cover during storage prior to use.The toothbrush assembly also comprises a handle initially assembledduring storage prior to use so as to extend a short distance into thehead at the mentioned transverse opening, the handle having a slightlyenlarged leading end, sized and shaped so as to spread the longitudinalside walls of the head during insertion, and including at the interfacebetween the enlarged leading end and the adjacent remainder of thehandle a notch along each side into which toothpaste flows duringinsertion to create a firm handle-retaining seal. The handle portionadjacent the mentioned enlarged leading end is sized and shaped so as toserve as a guide insuring proper alignment during insertion. Anextrusion channel is defined along the top of the leading end and thealignment or guide portions of the handle to accommodate flow oftoothpaste to the central port of the head after the leading end of thehandle has passed the port site.

13 Claims, 9 Drawing Figures PMENTEUAPRZZIQYS 3.879 1139 saw 1 n5 2PATENTEDAPRZZIQYS 3,879,139

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DIS POSABLE TOOTHBIRUSH ASSEMBLY BACKGROUND Continuity FIELD OFINVENTION This invention relates to the cleaning of teeth and moreparticularly to a disposable toothbrush assembly.

PRIOR ART Brushes have long been used for cleaning and polishing teeth,and like purposes. However, there have been many disadvantages to suchbrushes and their use heretofore. The storage of toothbrushes betweenuse periods presents contamination problems. Also, for sanitarypurposes, each person must have his own toothbrush and, in largefamilies, and-the like, substantial storage space is required and use ofthe wrong toothbrush becomes a frequent problem. In addition, it iscustomary to provide toothpaste in squeeze tubes which requireadditional storage space and, due to individual preferences, it isusually necessary for a family to store several such tubes. Furthermore,if toothpaste tubes are squeezed adjacent the dispensing end, ratherthan adjacent the remote end, it is difficult to dispense all of thetoothpaste from the tube and much of the contents of the tube is wasted.Another practice, which falls in the same category, is that of failingto replace the cap on the toothpaste tube, which allows the tooth pastein the dispensing neck of the tube to harden and prevents dispensing ofthe remainder of the contents. When travelling, the problems relating toconventional toothbrushes and toothpaste are increased. Toothbrushes andtoothpaste tubes often become misplaced and lost. Moreover, sincetoothbrushes are often wet and retain some toothpaste in their bristles,special containers or compartments must be provided, in suitcases andthe like, to prevent the toothbrushes from soiling or staining clothingor other articles packed therewith.

Numerous attempts have been made heretofore to overcome these problemsand to provide an approach insuring fresh breath, reduced cavities andbrushing capability without carrying the conventional brush and pastecontainer. However, none of the prior art devices has been entirelysatisfactory. Many attempts have been made to combine a toothbrush witha toothpaste dispenser. Unfortunately, many of the prior art deviceshave been complicated and expensive to produce. Loss of flavor and/orfreshness from the toothpaste with passage of time is likewise a problemwhen a toothbrush and toothpaste are in combination. Other prior artdevices have been difficult to use, while still others have beenextremely wasteful and often messy. Many of the prior art devices havefailed to overcome one or more of the problems stated above, and mayhave introduced additional problems.

BRIEF SUMMARY AND OBJECTS OF THE INVENTION The mentioned disadvantagesof the prior art are overcome or substantially alleviated with thepresent invention and a toothbrush assembly and related method areprovided, which assembly is simple and economical to produce and use,assures sanitation during storage and transportation, prevents waste andmessy loss of toothpaste, reduces the storage space required, overcomesthe problems of mix-up or loss, preserves the flavor and freshness ofthe toothpaste even when stored for a protracted period of time andinsures superior cleaning of the teeth when used.

The advantages of the present invention are preferably attained byproviding a toothbrush assembly and related methods, the toothbrushassembly having a telescopic handle initially extending a short distancethrough a transverse opening into the base of a head formed of pliableplastic with memory containing a supply of toothpaste in the baseadjacent external bristles which extend from the top face of the baseabout a central pre-cut but initially covered central port. Toothpasteis automatically extruded from its encasement in the base throughtheport, along a chimney formed by surrounding bristles and across thetop of the bristles upon insertion of the handle fully into the base.The interior of the base is longitudinally convergently tapered in thedirection of handle insertion and the leading end of the handle isslightly larger than the cross-sectional area of the base. Thus, as thehandle is axially advanced into the hollow interior of the base, beingguided by the side edges of the handle adjacent but downstream of theleading end of the handle, the base is expanded by but retracts behindthe enlarged leading end of the handle with a toothpaste seal beingformed between the handle and the base along the side edges at alocation where the handle is reduced adjacent the enlarged leading end.The more the handle is advanced into the base the more tightly it isretained against inadvertent removal during use, yet advancement createslittle resistances. An hydraulic extrusion channel at the upper face ofthe handle directs toothpaste back to the extrusion port once theleading end of the handle has passed the port. An extrusion channel sealis located inside the head and substantially fills the channel,preventing the paste from extruding down the channel and escaping ontothe handle.

With the foregoing in mind, it is a primary object of the presentinvention to provide an improved disposable toothbrush assembly forcleaning teeth, and related methods.

Another object of the present invention is to provide a toothbrushassembly comprising a base and telescopically insertable handle which issimple and economical to produce and use.

Another object of the present invention is the provision of a disposabletoothbrush assembly with toothpaste encased within the base of a headwhich preserves flavor and freshness, avoids contamination and minimizeswaste.

A further paramount object of the present invention is to provide adisposable toothbrush assembly having a head the base of which comprisesa pre-cut and initially covered central extrusion port to preservetoothpaste freshness but permits ready extrusion when use is desired.

A further significant object of the present invention is the provisionof a disposable toothbrush assembly comprising a novel head with atransverse opening and interior walls which are slightly convergentlytapered away from the opening.

A further significant object of the present invention is the provisionofa novel disposable toothbrush assembly comprising a head fabricated ofmaterial which will expand under force of handle insertion and return toits original dimensions because of the memory of the material.

It is a further and important object of the present invention to providea disposable toothbrush assembly comprising a handle the leading end ofwhich is enlarged in respect to the head into which it is telescopicallyforcibly inserted.

A further paramount object of the present invention is to provide anovel disposable toothbrush assembly comprising a handle comprising atleast one reduced diameter slot adjacent an enlarged leading end wherebyan hydraulic seal is formed with toothpaste initially contained within ahead.

A further primary object of the present invention is to provide animproved handle for a disposable toothbrush assembly wherein a centralportion of the handle serves as a guide to insure aligned insertion ofthe handle into a head, from which toothpaste is extruded.

Another principal object of the present invention is the provision of anovel handle for a disposable toothbrush assembly wherein an upperhydraulic extrusion channel is provided for back flow of toothpaste to acentral extrusion port in a head thereof.

Another valuable object of the present invention is the provision of anovel head as part of a disposable toothbrush, the head having aninternal seal at an extrusion channel in a handle to prevent loss ofpaste at the extrusion channel site.

These and other objects and features of the present invention will beapparent from the following detailed description, taken with referenceto the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective representationof a presently preferred disposable toothbrush assembly with the handleplaced in a transverse opening of the base of a disposable head forstorage and shipment prior to use;

FIG. 2 is an exploded perspective representation of the disposabletoothbrush assembly of FIG. 1;

FIG. 3 is a crosssectional view taken along lines 3-3 of FIG. 2;

FIG. 4 is a fragmentary plan view taken along lines 4-4 of FIG. 2;

FIG. 5 is a cross-sectional view taken along lines 55 of FIG. 2;

FIG. 6 is a fragmentary bottom plan view taken along lines 6-6 of FIG.5;

FIG. 7 is a longitudinal fragmentary cross section of the head and partof the handle of the disposable toothbrush assembly of FIG. 6 with thehandle inserted into the base of the head up to the central extrusionport;

FIG. 8 is a fragmentary cross-sectional view similar to FIG. 7 with thehandle further inserted into the head of the base illustrating thereverse flow of toothpaste to the extrusion port; and

FIG. 9 is a cross-section view of one bristle of the head of thedisposable toothbrush assembly of FIG. 1.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT In that form of thepresent invention chosen for purposes of illustration, FIGS. 1 and 2show a disposable toothbrush assembly, generally designated 10. Theassembly 10 comprises primarily a disposable head 12 and a disposablehandle 14. The head 12 is preferably fabricated as one piece usinginjection molding tech niques and comprises a hollow, generallybox-shaped base 16 which in turn comprises a trailing transverse opening18, generally rectangular in configuration, a bottom wall 20, atop wall22 and spaced longitudinally directed convergently tapered side walls24, the taper being away from the opening 18 to the leading trans versewall 26. The top and bottom walls 20 and 22 may also be slightlyconvergently tapered toward wall 26. In reference to FIG. 4, whichillustrates the convergence, it is presently preferred that the taper abeing on the order of 20.

The hollow cavity, with the exception of a short distance at opening 18within the base 16 is filled with a slug of toothpaste 28. It ispreferred that the slug of toothpaste 28 be inserted into a series ofheads 12 by causing a predetermined amount of toothpaste from a largesupply to be displaced through the opening 18. Naturally, the toothpasteis pliable and extrudable as initially placed within the hollow of thebase 16 and is preserved in that condition in a manner hereinafterdescribed.

A plurality of bristles 30 are integrally formed with and extendupwardly from the top face 22 of the base 16. The preferredcross-sectional configuration of the bristles is illustrated in FIG. 9whereby proper up and down strokes with the brush, once properlyassembled with the handle so as to provide toothpaste across the top ofthe bristles 30, will insure maximum bristle resistance and superiorscrubbing action. It has been found that bristles of the configurationshown in FIG. 9 produce improved dental hygiene which is superior tomany toothbrushes currently on the market and intended for repeatedrather than disposable use.

The top wall 22 of the base 16 comprises a rectangular opening or port32. Naturally, the port 32 could be otherwise configurated. The port 32is closed by a hinged valve cover 34 and it is preferred that the hingedvalve cover 34 be created by die punching the port 32 along three of thefour sides after the head 12 has been integrally injection molded. Thedie cutting technique must result in negligible space 36 at therectangular interface 36 between the hinged valve cover 34 and the port32. In this way, it has been found that the freshness (absence ofdryness and retention of flavor) of the toothpaste is preserved and yetthe extrusion of the paste from the cavity of the base 16 is readilyaccomplished without resistance. Upon handle insertion, the toothpaste28 contained within the hollow space 16 is immediately extruded upwardthrough the port 32 up the chimney 38 defined by the surroundingbristles and across the top of the bristles 30.

It is important that the plastic material from which the head 12 isformed be pliable and have considerable memory so that a stretchingeffect, hereinafter explained, during handle insertion will result in areturn by the material from which the head is fabricated to its initialdimensions in order to create stability between the head 12 and thehandle 14 following insertion and to create an improved seal between thehead and handle during and following insertion.

The handle 14 preferably comprises an elongated relatively thin onepiece item the trailing end 40 of which is intended to be held in thehand of the user. The forward portion 42 of the handle 14 is intended tobe inserted through the opening 18 into the hollow of the base 16.

A sealing compound, such as paraffin or gelatin or other suitablebiologically inert non-bonding compound may be initially interposedbetween the leading end portion of the handle and the interior wallsurfaces of the base adjacent the opening 18 to further aid inpreserving freshness. The same approach may be used to seal theinterface 36 between the port 32 and the closure hinged valve cover 34.

An enlarged abutment 44 is intended to function as a stop upon reachingthe opening 18, and 45 is a relief to aid in the comfort of the user byallowing the lips of user to close on handle. The forward portion 42 ofthe handle 14 comprises an enlarged leading end 46, a necked downportion 48 and a reduced sized guide portion 50. With reference to FIG.6, it is presently preferred that the distance T which is one-half thedifference in transverse dimension between the enlarged leading end 46and the guide portion 50 be on the order of 0.00l0.003 of an inch. Thetransverse dimension across necked down portion 48 is slightly less thanthe transverse dimension at 50.

An extrusion chamber 52 extends along the top surface of the forwardportion 42 of the handle 14 inclusive of the enlarged end 46, the neckeddown portion 48 and the guide portion 50 for a specific purposehereinafter more fully explained.

Disregarding the channel 52, the enlarged leading end 46 defines across-sectional area slightly larger than the cross-sectional area atopening 18 of base 16. The principal difference in the respectivecrosssectional area is caused primarily because of the greatertransverse dimension at leading end 46. Thus, when the leading end 46 ofhandle 14 is placed in the hollow of base 16 at opening 18, a spreadingeffect of the base side walls occurs as best illustrated in FIG. 6,which is a bottom plan view. As a result, the yieldable plastic materialfrom which the head 12 is made is displaced outwardly by the leading end46 as illustrated at locations 56, thereafter clings tightly to thesides 58 of the enlarged head 46 and later returns, because of thememory of the material from which the head 12 is made, to essentiallythe original dimensions when reaching the necked down and guide portions48 and 50.

To prevent paste loss at channel 52, an extrusion channel seal 53 isprovided along the inside of top wall 22 of base 16. The seal 53projects from wall 22 so as to entirely fill the channel 52 and firmlyengage all surfaces forming the channel 52.

As insertion increases, retention is primarily by plastic flowing(memory). Thus, the side walls 28 of the base 16 and the enlarged sideflanges 58 of the leading end 56 will flow into and rest at notches ornecked down portion 48, creating a seal which prohibits loss of pastealong the exposed portion of the handle 14 and aids in preventinginadvertent handle removal. As the handle 14 is further inserted, thebase 16 at opening 18 will contiguously grip the guide portion 50 of thehandle 14, serving to insure axial alignment between the head 12 and thehandle 14 during insertion. Also, because of the taper at wall 24, anadditional retaining force at locations 56 is created between theleading end 46 of the handle 14 and the head 12, the magnitude of whichincreases as insertion continues. Once insertion has been completed,firm retention against inadvertent separation is insured.

The forward portion 42 of the handle 14 comprises side wall flanges 60which extend both up and down along the leading end 46, the necked downportion 48 and the guide portion 50, although the thickness of theflange varies as illustrated. A front abutment flange 62 runningtransverse of the handle 14 at the leading end 46 serves to preventtoothpaste extrusion during insertion along the bottom of the handle.

The handle at the insertion segment 42 thereof accommodates a feedbackextrusion of toothpaste along the extrusion channel 52, once the leadingend 46 of the handle 14 has been displaced past the central extrusionport 32, insuring controlled extrusion of essentially all of thetoothpaste encased within the base 16 for use in brushing the teeth,thereby minimizing waste. Contrast FIG. 7 and 8.

It is presently preferred that the hinged valve cover 34 be cut orotherwise positioned prior to filling of the hollow of the base 16 withtoothpaste, the hinged valve cover 34 being held by suitable retainingstructure in the illustrated position during such filling, followingwhich the hinged valve cover 34 has been found to be self-retainingprior to handle insertion. Also, as illustrated in FIG. 1, it isessential for the preservation of taste freshness that the handle 14 beinserted a short distance through the opening 18 of the base 16 forstorage, shipment and the like prior to use.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by U.S. Letters Pat. is:

1. A disposable toothbrush assembly comprising:

a head formed from yieldable plastic material having memory comprising ahollow base defined by side walls, a bottom wall, a top wall and an endwall but open at the other transverse end, said head comprising aplurality of bristles extending from the top wall of the base, a portcentrally disposed in said top wall of the base interconnecting thebristles with the interior of the base, and a removable closuresubstantially filling the port;

a quantity of tooth cleansing or treating material disposed within andfilling essentially all of the hollow of the base except a shortdistance adjacent said base opening, the tooth material being contiguouswith the closure;

a separate handle formed of substantially rigid plastic material havingan enlarged leading end portion sized to enlarge the crosssectional areaof the base by expanding the yieldable plastic material as the handle istelescopically inserted into the hollow of the base, the handlecomprising a reduced size guide portion adjacent the leading end portionsized to allow yieldable plastic to flow and lock behind the enlargedsection to engage the side walls of the base to maintain axial alignmentbetween the base and handle during said insertion, memory of the basematerial constricting the base crosssectional area into said engagement,the handle comprising a tooth material extrusion chamber extendingacross the leading end portion and the guide portion whereby the toothmaterial flows back to the central port along the extrusion chamberafter the leading end portion of the handle passes the extrusion portduring insertion.

2. A disposable toothbrush assembly as defined in claim 1 wherein thehollow interior of the base has a cross-sectional area whichprogressively converges between the opening and the end wall.

3. A disposable toothbrush assembly as defined in claim 2 wherein theconverging cross-sectional area is caused at least in part by taperedside walls of the base.

4. A disposable toothbrush assembly as defined in claim 1 furthercomprising slot means interposed between the leading end and the guideportions of the handle whereby a seal and lock between the handle andthe base occur at the slot means due to plastic flow of the base.

5. A disposable toothbrush assembly as defined in claim 1 wherein theextrusion chamber is defined in part by two upwardly extending flangeseach simultaneously engaging the top wall and one side wall of the base.

6. A disposable toothbrush assembly as defined in claim 1 wherein theleading end portion of the handle comprises two side wall engagingflanges, each said flange also engaging the top wall and the bottomwall, and a transverse flange engaging the bottom wall and bridgingbetween the two side wall engaging flanges.

7. A disposable toothbrush assembly as defined in claim 1 furthercomprising a biologically inert sealing compound initially interposedbetween the leading end portion of the handle and the interior wallsurfaces of the base adjacent the opening.

8. A disposable toothbrush assembly as defined in claim 1 wherein eachbristle of the head is injection molded and has a diamond-shaped crosssection having a side-to-side dimension substantially greater than thelongitudinal dimension when viewed in cross section.

9. A disposable toothbrush assembly as defined in claim 1 furthercomprising a seal projecting from the inside of the base andsubstantially filling the extrusion chamber.

10. A disposable toothbrush assembly as defined in claim 1 wherein theconverging cross-sectional area is caused at least in part by taperedtop and bottom walls of the base.

11. A disposable toothbrush assembly as defined in claim I furthercomprising a biologically inert sealing compound initially interposedbetween the extrusion port and the closure.

12. A method of making a disposable toothbrush, the steps of:

molding a plastic head of yieldable synthetic resinous material having ahollow base open along one transverse end and bristles projecting fromone wall of the base outwardly;

removing part of the one wall of the base to form an extrusion portcentral of the array of bristles; covering the extrusion port with aclose tolerance closure;

holding the closure within the port and simultaneously filling thehollow interior of the base with toothpaste, except for a minorityvolume juxtaposed the opening;

placing the leading end of an elongated handle into the opening toengage and spread walls of the base causing an expansion incross-sectional area of the hollow of the base, whereby the leading endis sealed and retaomed to the walls of the base, for storage prior touse;

advancing the leading end of the handle into the hollow of the baseperpetuating said sealed and retained condition and extruding paste fromthe hollow of the base through the extrusion port and on to top of thebristles, at a point in time when use is desired.

13. A method as defined in claim 12 wherein the advancing and extrudingcomprises initially forcing paste in the hollow of the base forwardtoward the extrusion port and later backward along extrusion chamber ofthe leading end of the handle to the extrusion port, once the leadingend has been displaced beyond the extrusion port.

1. A disposable toothbrush assembly comprising: a head formed fromyieldable plastic material having memory comprising a hollow basedefined by side walls, a bottom wall, a top wall and an end wall butopen at the other transverse end, said head comprising a plurality ofbristles extending from the top wall of the base, a port centrallydisposed in said top wall of the base interconnecting the bristles withthe interior of the base, and a removable closure substantially fillingthe port; a quantity of tooth cleansing or treating material disposedwithin and filling essentially all of the hollow of the base except ashort distance adjacent said base opening, the tooth material beingcontiguous with the closure; a separate handle formed of substantiallyrigid plastic material having an enlarged leading end portion sized toenlarge the cross-sectional area of the base by expanding the yieldableplastic material as the handle is telescopically inserted into thehollow of the base, the handle comprising a reduced size guide portionadjacent the leading end portion sized to allow yieldable plastic toflow and lock behind the enlarged section to engage the side walls ofthe base to maintain axial alignment between the base and handle duringsaid insertion, memory of the base material constricting the basecrosssectional area into said engagement, the handle comprising a toothmaterial extrusion chamber extending across the leading end portion andthe guide portion whereby the tooth material flows back to the centralport along the extrusion chamber after the leading end portion of thehandle passes the extrusion port during insertion.
 1. A disposabletoothbrush assembly comprising: a head formed from yieldable plasticmaterial having memory comprising a hollow base defined by side walls, abottom wall, a top wall and an end wall but open at the other transverseend, said head comprising a plurality of bristles extending from the topwall of the base, a port centrally disposed in said top wall of the baseinterconnecting the bristles with the interior of the base, and aremovable closure substantially filling the port; a quantity of toothcleansing or treating material disposed within and filling essentiallyall of the hollow of the base except a short distance adjacent said baseopening, the tooth material being contiguous with the closure; aseparate handle formed of substantially rigid plastic material having anenlarged leading end portion sized to enlarge the cross-sectional areaof the base by expanding the yieldable plastic material as the handle istelescopically inserted into the hollow of the base, the handlecomprising a reduced size guide portion adjacent the leading end portionsized to allow yieldable plastic to flow and lock behind the enlargedsection to engage the side walls of the base to maintain axial alignmentbetween the base and handle during said insertion, memory of the basematerial constricting the base cross-sectional area into saidengagement, the handle comprising a tooth material extrusion chamberextending across the leading end portion and the guide portion wherebythe tooth material flows back to the central port along the extrusionchamber after the leading end portion of the handle passes the extrusionport during insertion.
 2. A disposable toothbrush assembly as defined inclaim 1 wherein the hollow interior of the base has a cross-sectionalarea which progressively converges between the opening and the end wall.3. A disposable toothbrush assembly as defined in claim 2 wherein theconverging cross-sectional area is caused at least in part by taperedside walls of the base.
 4. A disposable toothbrush assembly as definedin claim 1 further comprising slot means interposed between the leadingend and the guide portions of the handle whereby a seal and lock betweenthe handle and the base occur at the slot means due to plastic flow ofthe base.
 5. A disposable toothbrush assembly as defined in claim 1wherein the extrusion chamber is defined in part by two upwardlyextending flanges each simultaneously engaging the top wall and one sidewall of the base.
 6. A disposable toothbrush assembly as defined inclaim 1 wherein the leading end portion of the handle comprises two sidewall engaging flanges, each said flange also engaging the top wall andthe bottom wall, and a transverse flange engaging the bottom wall andbridging between the two side wall engaging flanges.
 7. A disposabletoothbrush assembly as defined in claim 1 further comprising abiologically inert sealing compound initially interposed between theleading end portion of the handle and the interior wall surfaces of thebase adjacent the opening.
 8. A disposable toothbrush assembly asdefined in claim 1 wherein eacH bristle of the head is injection moldedand has a diamond-shaped cross section having a side-to-side dimensionsubstantially greater than the longitudinal dimension when viewed incross section.
 9. A disposable toothbrush assembly as defined in claim 1further comprising a seal projecting from the inside of the base andsubstantially filling the extrusion chamber.
 10. A disposable toothbrushassembly as defined in claim 1 wherein the converging cross-sectionalarea is caused at least in part by tapered top and bottom walls of thebase.
 11. A disposable toothbrush assembly as defined in claim 1 furthercomprising a biologically inert sealing compound initially interposedbetween the extrusion port and the closure.
 12. A method of making adisposable toothbrush, the steps of: molding a plastic head of yieldablesynthetic resinous material having a hollow base open along onetransverse end and bristles projecting from one wall of the baseoutwardly; removing part of the one wall of the base to form anextrusion port central of the array of bristles; covering the extrusionport with a close tolerance closure; holding the closure within the portand simultaneously filling the hollow interior of the base withtoothpaste, except for a minority volume juxtaposed the opening; placingthe leading end of an elongated handle into the opening to engage andspread walls of the base causing an expansion in cross-sectional area ofthe hollow of the base, whereby the leading end is sealed and retaomedto the walls of the base, for storage prior to use; advancing theleading end of the handle into the hollow of the base perpetuating saidsealed and retained condition and extruding paste from the hollow of thebase through the extrusion port and on to top of the bristles, at apoint in time when use is desired.